When supplying web uninterruptedly to a web consuming machine such as a printing press, for example, it is necessary to draw the web from a succession of rolls. When one web roll is exhausted, the trailing end of the web on that roll is spliced automatically to the leading end of a fresh web roll maintained at the ready. In some splicers, a pair of web rolls are arranged to be mounted underneath the bridge of the splicer. While web is drawn from one roll through the splicing station into the web consuming machine, the leading edge of web from the other roll is prepared for the next splice.
In order to facilitate such preparation, provision is often made for positioning the leading edge of the ready web at an accessible location out from under the splicer bridge. This is done in a variety of ways. Sometimes the web rolls are mounted on roll stands which can be rolled out to positions in front of bridge. Thus while web is drawn from a roll mounted on one roll stand located at the splicing station under the bridge, the other roll stand is rolled out so that a fresh web roll can be mounted on that stand and its leading end prepared for the next splice. Then that stand is rolled back under the bridge to await the next splice station.
If the web rolls are mounted on a so-called fixed stand, the leading end of the ready web can be prepared at an accessible location at an end of the bridge and then carried by suitable transport means into the splicing station prior to the time for making the next splice. These various kinds of splicers are described in U.S. Pat. No. Re. 29,365 owned by the assignee of the present application.
Prior to a splice, the ready horizontal positioning bar is moved to its accessible web preparation position. The leading end of web from the ready roll is aligned with and removably secured to the positioning bar. Next, a strip of double-faced adhesive tape is placed across the exposed face of the ready web end and the end margin beyond the tape is trimmed away. Then the positioning bar is moved back to the splicing station under the bridge so that the positioning bar positions the leading end of the ready web directly opposite the running web so that at the appropriate time the two webs can be pressed together to effect the splice.
Heretofore, two techniques have been used to secure the ready web end margin to the positioning bar prior to the taping and trimming steps described above. In one arrangement, a row of orifices are provided in the positioning bar and a vacuum drawn at those orifices which draws the web end against the bar and maintains its position thereon. That type of arrangement is not too satisfactory because it requires a vacuum pump on each roll stand and fluid-tight connections between the pump and the bar which tend to be relatively expensive. Also the orifices in the bar and the connections thereto tend to be occluded by the web fibers and other debris commonly present in the vicinity of web splicers. As a result, sometimes the web is not securely fastened to the positioning bar across its entire width which may cause a faulty splice.
In other splicing apparatus, the web end margin is secured to the positioning bar by strips of adhesive tape. The web end is aligned with and temporarily clamped to the face of the bar. Then a web end segment projecting above the bar is trimmed away at the bar edge. Next, several short tape strips are applied to the exposed face of the web end at spaced-apart locations thereacross with ends of the strips engaging over and adhering to the top of the bar. Following removal of the clamps, a strip of double-faced adhesive tape is applied to the exposed face of the web just below its leading edge to adhere the ready web to the running web at the appropriate time during a splice sequence.
The cleaning of old adhesive from the bar and the application of all the tape strips to the ready web and bar are tedious and time-consuming tasks. Also, the relative adherances of the short single-face tape strips and the double-faced strip can be quite critical. At the time of splice, the running web should become adhered to the double-faced tape with a sufficiently strong bond that the running web pulls the ready web edge and the short tape segments from the positioning bar. However, that does not always take place. Rather, sometimes the bonds at the double-faced tape give way before the ready web separates from the bar across its full width resulting in a faulty or completely missed splice. Also in many instances, tape strip segments carried along with the ready web adhere to downstream rollers and other machine parts causing tension upsets and marking of the web.
It would be desirable, then, to provide a means for securing the leading end of a ready web to a web positioning bar so that the web end releases properly from the bar across its entire width at the time of the splice and which is easy and inexpensive to implement and to operate.